Intraventricular dyssynchrony corresponds to the non-uniform activation (i.e., contraction) of, for example, left ventricle (LV) walls and has been shown to be predictive of major cardiac events, such as asymmetric muscle hypertrophy, caused by the increased work in late-activated regions. Other consequences include reductions in contractility, filling time, and ejection fraction. Increased recognition of the relationship between dyssynchrony and heart failure has led to cardiac resynchronization therapy (CRT), which has provided positive results in restoring ventricular function. By restoring coordinated contraction through multiple pacing sites, CRT can dramatically improve survival and quality of life for some patients. Response to CRT, however, is variable and, in the past, has been difficult to predict. For example, studies have shown that over 30 percent of patients receiving CRT may not respond to the treatment.
Based on the foregoing, accurate detection of intraventricular dyssynchrony is not well established. This may be in part due to insufficient characterization of intraventricular dyssynchrony by current diagnostic techniques. For example, selection of patients for CRT has been based on electrocardiography measurements of QRS duration (≧130 ms) and ejection fraction (≦35%). Clinical issues associated with CRT have also arisen, for example, in conjunction with determining the appropriate number of pacing leads and lead placement.
Information related to attempts to address these problems can be found, for example, in PCT Patent Application Publication Number WO 2006/042039 and U.S. Pat. Nos. 6,978,184 and 7,041,061. However, each one of these references requires insertion of a medical instrument (e.g., catheter) or implantation of a medical device (e.g., pacemaker, CRT device, etc.) in the patient in order to test for dyssynchrony. Based at least on the foregoing, there is a need for an improved method and apparatus for detecting intraventricular dyssynchrony.